The present invention relates generally to implantable prosthetic cardiac and venous valves. More particularly, the present invention pertains to prosthetic cardiac and venous valve implants which are capable of being delivered using endovascular techniques and being implanted at an intracardiac or intravenous site without the need for anatomic valve removal. The prosthetic valves of the present invention are well-suited for cardiac delivery via a femoral or subclavian artery approach using a delivery catheter, and, depending upon the specific configuration selected, may be deployed within the heart to repair valve defects or disease or septal defects or disease. According to one embodiment of the invention, there is provided a chamber-to-vessel (CV) configuration which is particularly well-suited as an aortic valve prosthesis to facilitate blood flow from the left ventricle to the aorta. In a second embodiment, there is provided a prosthetic valve in a chamber-to-chamber (CC) configuration which is particularly well-adapted for mitral valve replacement or repair of septal defects. Finally, a third embodiment is provided in a vessel-to-vessel (VV) configuration, which is well suited for venous valve exclusion and replacement.
Common to each of the CV, CC and VV embodiments of the present invention are a stent support member, a graft member which covers at least a portion of either or both the lumenal and ablumenal surfaces of the stent, valve flaps which are formed either by biological xenograft valves, synthetic valves formed from either the same material or a different material as the graft member, the valve flaps being coupled to the stent in a manner which biases the valve flaps so they close upon a zero pressure differential across the valve region.
It is important for the present invention to provide orientational definitions. For purposes of the present invention, references to positional aspects of the present invention will be defined relative to the directional flow vector of blood flow through the implantable device. Thus, the term xe2x80x9cproximalxe2x80x9d is intended to mean on the inflow or upstream flow side of the device, while xe2x80x9cdistalxe2x80x9d is intended to mean on the outflow or downstream flow side of the device. With respect to the catheter delivery system described herein, the term xe2x80x9cproximalxe2x80x9d is intended to mean toward the operator end of the catheter, while the term xe2x80x9cdistalxe2x80x9d is intended to mean toward the terminal end or device-carrying end of the catheter.
The prior art discloses certain common device segments inherently required by a percutaneous prosthetic valve: an expandable stent segment, an anchoring segment and a flow-regulation segment.
Prior art percutaneous prosthetic valve devices include the Dobben valve, U.S. Pat. No. 4,994,077, the Vince valve, U.S. Pat. No. 5,163,953, the Teitelbaum valve, U.S. Pat. No. 5,332,402, the Stevens valve, U.S. Pat. No. 5,370,685, the Pavcnik valve, U.S. Pat. No. 5,397,351, the Taheri valve, U.S. Pat. No. 5,824,064, the Anderson valves, U.S. Pat. Nos. 5,411,552 and 5,840,081, the Jayaraman valve, U.S. Pat. No. 5,855,597, the Besseler valve, U.S. Pat. No. 5,855,601, the Khosravi valve, U.S. Pat. No. 5,925,063, the Zadano-Azizi valve, U.S. Pat. No. 5,954,766, and the Leonhardt valve, U.S. Pat. No. 5,957,949. Each of these pre-existing stent valve designs has certain disadvantages which are resolved by the present invention.
The Dobben valve has a disk shaped flap threaded on a wire bent like a safety pin to engage the vessel wall and anchor the valve. A second embodiment uses a stent of a cylindrical or crown shape that is made by bending wire into a zigzag shape to anchor the device and attach the flow regulator flap. The device presents significant hemodynamic, delivery, fatigue and stability disadvantages.
The Vince valve has a stent comprised of a toroidal body formed of a flexible coil of wire and a flow-regulation mechanism consisting of a flap of biologic material. Numerous longitudinal extensions within the stent are provided as attachment posts to mount the flow-regulation mechanism. The device requires balloon expansion to deliver to the body orifice. The main shortcoming of this design is delivery profile. Specifically, the device and method put forth will require a 20+ French size catheter (approximately 9 French sizes to accommodate the balloon and 14+ French sizes to accommodate the compressed device) making the device clinically ineffective as a minimally invasive technique. Additionally, the device does not adequately address hemodynamic, stability and anchoring concerns.
The Teitelbaum valve is made of shape memory nitinol and consists of two components. The first component is stent-like and comprised of a meshwork or braiding of nitinol wire similar to that described by Wallsten, U.S. Pat. No. 4,655,771, with trumpet like distal a proximal flares. The purpose of the stent is to maintain a semi-ridged patent channel through the diseased cardiac valve after initial balloon dilation. The flared ends are intended to maintain the position of the stent component across the valve thereby anchoring the device. Embodiments for the flow-regulation mechanism include a sliding obturator and a caged ball both which are delivered secondary to the stent portion. The disadvantages of the device are the flow regulators reduce the effective valve orifice and generate sub-optimal hemodynamic characteristics; fatigue concerns arise from the separate nature of the stent and flow-regulation components; the high metal and exposed metal content raises thrombogenesis, valvular stenosis and chronic anticoagulation concerns; and the separate delivery requirements (although addressing the need for small delivery profile) in addition to any initial valvuloplasty performed increases the time, costs, risks, difficulty and trauma associated with the percutaneous procedure.
The Pavcnik valve is a self-expanding percutaneous device comprised of a poppet, a stent and a restraining element. The valve stent has barbed means to anchor to the internal passageway. The device includes a self-expanding stent of a zigzag configuration in conjunction with a cage mechanism comprised of a multiplicity of crisscrossed wires and a valve seat. The disadvantages of the device include large delivery profile, reduced effective valvular orifice, possible perivalvular leakage, trauma-inducing turbulent flow generated by the cage occlusive apparatus and valve seat, thrombogenesis, valvular stenosis, chronic anticoagulation, problematic physiological and procedural concerns due to the barb anchors and complex delivery procedure that includes inflation of occlusive member after initial implantation.
Stevens discloses a percutaneous valve replacement system for the endovascular removal of a malfunctioning valve followed by replacement with a prosthetic valve. The valve replacement system may include a prosthetic valve device comprised of a stent and cusps for flow-regulation such as a fixed porcine aortic valve, a valve introducer, an intraluminal procedure device, a procedure device capsule and a tissue cutter. The devices disclosed indicate a long and complex procedure requiring large diameter catheters. The valve device disclosed will require a large delivery catheter and does not address the key mechanisms required of a functioning valve. Additionally, the device requires intraluminal-securing means such as suturing to anchor the device at the desired location.
The Taheri valve describes an aortic valve replacement combined with an aortic arch graft. The devices and percutaneous methods described require puncture of the chest cavity.
Anderson has disclosed various balloon expandable percutaneous prosthetic valves. The latest discloses a valve prosthesis comprised of a stent made from an expandable cylindrical structure made of several spaced apices and an elastically collapsible valve mounted to the stent with the commissural points of the valve mounted to the apices. The device is placed at the desired location by balloon expanding the stent and valve. The main disadvantage to this design is the 20+ French size delivery requirement. Other problems include anchoring stability, perivalvular leakage, difficult manufacture and suspect valve performance.
The Jayaraman valve includes a star-shaped stent and a replacement valve and/or replacement graft for use in repairing a damaged cardiac valve. The device is comprised of a chain of interconnected star-shaped stent segments in the center of which sits a replacement valve. The flow-regulation mechanism consists of three flaps cut into a flat piece of graft material that is rolled to form a conduit in which the three flaps may be folded inwardly in an overlapping manner. An additional flow-regulation mechanism is disclosed in which a patch (or multiple patches) is sutured to the outside of a conduit which is then pulled inside out or inverted such that the patch(s) reside on the fully inverted conduit. A balloon catheter is required to assist expansion during delivery. The disadvantages of this design include lack of sufficient anchoring mechanism; problematic interference concerns with adjacent tissues and anatomical structures; fatigue concerns associated with the multiplicity of segments, connections and sutures; lack of an adequately controlled and biased flow-regulation mechanism; uncertain effective valve orifice, difficult manufacture; balloon dilation requirement; complex, difficult and inaccurate delivery and large delivery profile.
The Besseler valve discloses methods and devices for the endovascular removal of a defective heart valve and the replacement with a percutaneous cardiac valve. The device is comprised of a self-expanding stent member with a flexible valve disposed within. The stent member is of a self-expanding cylindrical shape made from a closed wire in formed in a zigzag configuration that can be a single piece, stamped or extruded or formed by welding the free ends together. The flow-regulation mechanism is comprised of an arcuate portion which contains a slit (or slits) to form leaflets and a cuff portion which is sutured to and encloses the stent. The preferred flow regulator is a porcine pericardium with three cusps. An additional flow regulator is described in which the graft material that comprises the leaflets (no additional mechanisms for flow-regulation) extends to form the outer cuff portion and is attached to the stent portion with sutures. The anchoring segment is provided by a plurality of barbs carried by the stent (and therefor penetrating the cuff-graft segment). Delivery requires endoluminal removal of the natural valve because the barb anchors will malfunction if they are orthotopically secured to the native leaflets instead of the more rigid tissue at the native annulus or vessel wall. Delivery involves a catheter within which the device and a pusher rod are disposed. The disadvantages of the device are lack of a well defined and biased flow-regulation mechanism, anatomic valve removal is required thereby lengthening the procedure time, increasing difficulty and reducing clinical practicality, trauma-inducing barbs as described above and the device is unstable and prone to migration if barbs are omitted.
The Khosravi valve discloses a percutaneous prosthetic valve comprised of a coiled sheet stent similar to that described by Derbyshire, U.S. Pat. No. 5,007,926, to which a plurality of flaps are mounted on the interior surface to form a flow-regulation mechanism that may be comprised of a biocompatible material. The disadvantages of this design include problematic interactions between the stent and flaps in the delivery state, lack of clinical data on coiled stent performance, the lack of a detailed mechanism to ensure that the flaps will create a competent one-directional valve, lack of appropriate anchoring means, and the design requirements imposed by surrounding anatomical structures are ignored.
The Zadno-Azizi valve discloses a device in which flow-regulation is provided by a flap disposed within a frame structure capable of taking an insertion state and an expanded state. The preferred embodiment of the flow-regulation mechanism is defined by a longitudinal valve body made of a sufficiently resilient material with a slit(s) that extends longitudinally through the valve body. Increased sub-valvular pressure is said to cause the valve body to expand thereby opening the slit and allowing fluid flow there through. The valve body extends into the into the lumen of the body passage such that increased supra-valvular pressure will prevent the slit from opening thereby effecting one-directional flow. The device includes embedding the frame within the seal or graft material through injection molding, blow molding and insertion molding. The disadvantages of the device include the flow-regulation mechanism provides a small effective valve orifice, the turbidity caused by the multiple slit mechanisms, the large delivery profile required by the disclosed embodiments and the lack of acute anchoring means.
Finally, the Leonhardt valve is comprised of a tubular graft having radially compressible annular spring portions and a flow regulator, which is preferably a biological valve disposed within. In addition to oversizing the spring stent by 30%, anchoring means is provided by a light-activated biocompatible tissue adhesive is located on the outside of the tubular graft and seals to the living tissue. The stent section is comprised of a single piece of superelastic wire formed into a zigzag shape and connected together by crimping tubes, adhesives or welds. A malleable thin-walled, biocompatible, flexible, expandable, woven fabric graft material is connected to the outside of the stent that is in turn connected to the biological flow regulator. Disadvantages of this device include those profile concerns associated with biological valves and unsupported graft-leaflet regulators, a large diameter complex delivery system and method which requires multiple anchoring balloons and the use of a light activated tissue adhesive in addition to any prior valvuloplasty performed, interference with surrounding anatomy and the questionable clinical utility and feasibility of the light actuated anchoring means.
With the shortcomings of the prior art devices, there remains a need for a clinically effective endoluminally deliverable prosthetic valve that is capable of orthotopic delivery, provides a mechanically defined, biased and hemodynamically sound flow-regulation mechanism, provides sufficient force to maintain a large acute effective valvular orifice dimension which expands to a known larger effective orifice dimension, compliant with adjacent dynamic anatomical structures, does not require valve removal, does not require chronic anticoagulation treatment, meets regulatory fatigue requirements for cardiac valve prostheses, provides a low-metal high-strength stent-annulus, is surgically explantable or endoluminally removable, in addition to being able to deploy multiple valves orthotopically, provides a delivery profile which does not exceed the 12 French size suitable for peripheral vascular endoluminal delivery, combines anatomic valve exclusion and prosthetic valve delivery via a single catheter delivery system and with short duration atraumatic procedure which is easy to complete and beneficial to very sick patients.
It is, therefore, a primary of the present invention to provide a prosthetic endoluminally-deliverable unidirectional valve. The invention has multiple configurations to treat malfunctioning anatomical valves including heart and venous valves. Prosthetic cardiac valve configurations include the chamber-to-vessel for orthotopic placement at the valvular junction between a heart chamber and a vessel, and the chamber-to-chamber for orthotopic placement at the valvular junction between two heart chambers or for septal defect repair where a septal occluding member is substituted for the flow regulator valve flaps. Prosthetic venous valve configurations include the vessel-to-vessel for orthotopic or non-orthotopic placement at a valvular junction within a vessel.
The invention consists generally of a stent body member, a graft, and valve flaps. The stent body member may be fashioned by laser cutting a hypotube or by weaving wires into a tubular structure, and is preferably made from shape memory or super-elastic materials, such as nickel-titanium alloys known as NITINOL, but may be made of balloon expandable stainless steel or other plastically deformable stent materials as are known in the art, such as titanium or tantalum, or may be self-expanding such as by weaving stainless steel wire into a stressed-tubular configuration in order to impart elastic strain to the wire. The graft is preferably a biocompatible, fatigue-resistant membrane which is capable of endothelialization, and is attached to the stent body member on at least portions of either or both the lumenal and ablumenal surfaces of the stent body member by suturing to or encapsulating stent struts. The valve leaflets are preferably formed by sections of the graft material attached to the stent body member.
The stent body member is shaped to include the following stent sections: proximal and distal anchors, a intermediate annular stent section, and at least one valve arm or blood flow regulator struts. The proximal and distal anchor sections are present at opposing ends of the prosthesis and subtend either an acute, right or obtuse angle with a central longitudinal axis that defines the cylindrical prosthesis. In either the CV or CC configurations, the proximal anchor is configured to assume approximately a right angle radiating outward from the central longitudinal axis of the prosthesis in a manner which provides an anchoring flange. When being delivered from a delivery catheter, the proximal anchor is deployed first and engages the native tissue and anatomical structures just proximal to the anatomic valve, such as the left ventricle wall in the case of retrograde orthotopic delivery at the aortic valve. Deployment of the proximal anchor permits the intermediate annular stent section to be deployed an reside within the native valve annular space and the ablumenal surface of the intermediate annular stent section to abut and outwardly radially compress the anatomic valve leaflets against the vascular wall. The distal anchor is then deployed and radially expands to contact the vascular wall and retain the prosthesis in position, thereby excluding the anatomic valve leaflets from the bloodflow and replacing them with the prosthetic valve leaflets.
Flow regulation in the inventive stent valve prosthesis is provided by the combination of the prosthetic valve leaflets and the valve arms and is biased closed in a manner similar manner to that described for a surgically implanted replacement heart valve by Boretos, U.S. Pat. No. 4,222,126. The valve regulator-struts are preferably configured to be positioned to radiate inward from the stent body member toward the central longitudinal axis of the prosthesis. The graft-leaflet has the appearance of a partially-everted tube where the innermost layer, on the lumenal surface of the stent body member, forms the leaflets and the outer-most layer, on the ablumenal surface of the stent body member, forms a sealing graft which contacts and excludes the immobilized anatomical valve leaflets. The struts of the stent are encapsulated by the outer graft-membrane. The valve regulator-struts are encapsulated by the inner leaflet-membrane and serve to bias the valve to the closed position. The regulator-struts also prevent inversion or prolapse of the otherwise unsupported leaflet-membrane during increased supra-valvular pressure. The inner leaflet-membrane may also be attached to the outer graft-membrane at points equidistant from the valve strut-arms in a manner analogous to that described for a surgically implanted replacement heart valve by Cox, U.S. Pat. No. 5,824,063. The combination of the thin walled properties of the leaflet-membrane, the one-sided open lumen support of the intermediate annular stent section, the free ends of the valve leaflets, the biasing and support provided by the valve regulator-struts and the attachment points all work to provide a prosthetic valvular device capable of endoluminal delivery which simulates the hemodynamic properties of a healthy anatomical cardiac or venous valve.